The present invention relates to contact structures of high voltage circuit breakers. More specifically, contact structures using an interposed solid nonconductor to extinguish the arc.
The interruption of DC high voltage, high current circuits is particularly difficult due to the lack of periodically occurring current zero crossings. Arcs exhibit a negative resistance characteristic in that the arc voltage decreases with increasing current. Consequently, switch contact arcs of more than a few amperes require little voltage to maintain, and, without an arc quenching means, will continue to quickly destroy the switch contacts. The arc is extinguished by using techniques that cause a momentary current zero or techniques that raise the voltage required to maintain the arc above the voltage available or by breaking the arc into a series of short arcs.
Conventional devices use different methods for accomplishing one or more of these basic arc quenching techniques. However, most of the high voltage high current switches now in use require the use of sulfur hexafluoride, a potent greenhouse gas considered nearly 25,000 times more damaging to the environment than carbon dioxide.
Contact structures can be found in Harton et al., U.S. Pat. No. 3,053,945, and Fisher, U.S. Pat. No. 3,026,396. However, neither of those devices is intended to open active high current circuits, only to reliably isolate circuits after an additional breaker has interrupted the main load circuit.